The method relates to a method for producing a fully transposed composite superconductor with an at least approximately rectangular cross section, which contains two or more conductor elements that are combined in the form of a transposed conductor bar, are composed of high-Tc superconductor material and each have an at least approximately rectangular cross section with a width B. In the method, the conductor elements are produced in a shape with a lateral projection, on the plane of the width B, into an area of an adjacent conductor element, and the conductor elements are twisted with one another. The invention also relates to a conductor produced using this method. A conductor such as this and the method for its production are disclosed in WO 01/59909.
High-power applications of high-Tc superconductors (referred to as HTC conductors in the following text), for example in order to produce a transformer, machine or other magnet windings, require low-loss conductors with alternating-current ratings up to the kiloamp range. In the past, only small cross section HTC ribbon conductors have been available, with current carrying capacities of up to a few 100 Aeff at 77 K in their own magnetic field. Furthermore, these ribbon conductors are mechanically highly sensitive, and their electrical characteristics are strongly dependent on the magnitude and the direction of the local magnetic field in which they are located.
There is therefore good reason to construct technically useable high-current superconductors composed of a large number of individual, parallel ribbon conductors, in the form of so-called composite conductors, for example according to DE 27 36 157 B2. Furthermore, the ribbon conductors (which are referred to in the following text as conductor elements or individual conductors) of such composite conductors are isolated from one another and are systematically transposed or twisted for alternating-current applications at industrial frequencies (in general up to 60 Hz), in order in this way to ensure a uniform current distribution throughout the entire cross section, and low alternating-current losses associated with this.
Corresponding transposed composite conductors, which are also referred to as twisted conductors or cable conductors, with a high alternating-current carrying capacity are in principle known. They may be designed as follows:                as so-called “conductor bars”, for example in the form of transposed conductor bars or transposed conductors, with conductor elements composed of copper, for example for large alternating-current machines,        as so-called “twisted conductors”, with conductor elements composed of copper for transformers or inductors, or        as so-called transposed “flat or round conductors” with conductor elements composed of metallic superconductors such as NbTi in copper (see the cited DE 27 36 157 B2).        
In principle, transposition of HTC conductors is also known, in order to increase the alternating-current carrying capacity. In this context, specific configuration analyses and design information relate to:                continuous transposition of round or virtually round HTC conductors to form single or multiple cables (see, for example, the so-called “Rutherford Cable” in “IEEE Trans. Appl. Supercond.”, Vol. 7, No. 2, June 1997, pages 958 to 961),        achievement of a continuous transposition effect in power cables by variation of the pitch of twisted ribbon HTC conductor elements from one conductor layer to the next (so-called “Pitch Adjustment”; see WO 96/39705), and        so-called “in-situ transposition”, that is to say step-by-step transposition during winding production directly on a winding former, for example a transformer winding (see, for example, “IEEE Trans. Appl. Supercond.”, Vol. 7, No. 2, June 1997, pages 298 to 301).        
One possible embodiment of a fully transposed HTC composite superconductor with an at least approximately rectangular cross section, which contains two or more conductor elements combined in the form of a transposed conductor bar, as well as an apparatus for its production can be found in WO 01/59909 A1, which was cited in the introduction. One characteristic of this composite conductor is lateral bending of its ribbon conductor elements with a predetermined bending radius and a predetermined bending zone length. The production of the corresponding “upright bending zones”, in which a change takes place to an area of an adjacent conductor element, is in this case carried out during the process of transposition. This process requires specific minimum dimensions with respect to the bending radii and bending zones, specifically, for each conductor element, a bending radius R which is greater than one hundred times the width B of the conductor element, and a bending or changeover zone length H which is greater than twenty times the width B. The full-transposition length of the known HTC composite conductor is therefore relatively large. The ribbon conductor elements which contain a HTC material based on the BiSrCaCuO system are preferably used for this purpose. Corresponding conductor elements generally have cores composed of this HTC material which are embedded in a normally conductive matrix, preferably composed of silver or of a silver alloy.
In addition to such single-core or multicore conductors (or conductor elements), corresponding HTC conductors in ribbon form may also be produced by coating a ribbon support on one or both sides with an HTC material (see, for example, “Physica C”, Volumes 185 to 189, 1991, pages 1959 to 1960; “Appl. Phys. Left.”, Volume 65, No. 15, Oct. 10, 1994, pages 1961 to 1963; “Appl. Phys. Left.”, Volume 71, No. 18, Nov. 3, 1997, pages 2695 to 2697 or WO 00/46863). However, conductors such as these cannot be used without further measures for a design based on the known HTC composite conductor, since there is a risk there of damage to the HTC layer that is applied to the mounting ribbon, as a result of the upright bending step.